Parameter --pull-request-body don't pass content to Pull Requests

[klemis]

According to the documentation there is a parameter --pull-request-body to insert a PR body using jx-updatebot pr command. I looked at the code and it requires both --pull-request-body and --commit-message (not empty) to be able to display body in Pull Request, but in fact, the content of --commit-message is passed to the PR body instead of content of --pull-request-body.